A multinuclear NMR study of ion transport in P(EO)nLiBETI complexes

A study of ion transport in P(EO)(n)LiBETI complexes was undertaken, using both AC impedance and nuclear magnetic resonance (NMR) spectroscopy. H-1, Li-7 and F-19 NMR techniques were used to investigate structure and dynamics as a function of tempera re for n=3, 6, and 20. Spin-lattice relaxation times (T-1) and spectral information were obtained from -50 to 100 degrees C. Variable temperature self-diffusion coefficients (D) and ionic conductivity (sigma) measurements were also performed. Anion diffusion (D-F) results displayed a dependence on available free volume, increasing with decreasing salt concentration. On the other hand, cation diffusion (D-Li) results did not follow this trend. D-Li for n=3 and 6 suggest the presence of ionic mobility in the crystalline phase, with a significant rise above the melting point. A transition from a crystalline to amorphous phase dominated ion transport occurs at n=8. This is supported by sigma results, which exhibited a VTF type of behavior for n >= 8 that is associated with ion transport in the amorphous phase. (c) 2005 Elsevier B.V. All rights reserved.